GamerDad has a review of all the premium modules released for Neverwinter Nights. Those would be the little mini-modules that you get to pay to play. While the author liked most of the modules with the exception of one, here's something I thought was kind of off:

One bad thing that "Premium" currently means is that you have to stay connected to the internet so the module can verify ownership every time you start the module or load a saved game.